An X-ray generally indicates a short, wavelength electromagnetic wave having a wavelength of 0.01 nm to 10 nm and a frequency of 30×1015 Hz to 30×1018 Hz. X-ray photographing is one of radiographics of projecting and displaying an inner portion of an object to be inspected by high penetration power of the X-ray. As well-known, the X-ray involves an attenuation phenomenon depending on a material, a density, and a thickness of an object, such as Compton scattering, a photoelectric effect, or the like, during a process in which it is transmitted through the object. Therefore, the X-ray photographing projects and displays the inner portion of the object to be inspected on the basis of an attenuation amount of the X-ray accumulated during a process in which the X-ray passes through the object to be inspected. To this end, a dedicated X-ray system is used.
Recently, an X-ray image technology has been rapidly evolved as a digital X-ray image technology having various advantages such as a relatively high resolution, a wide dynamic area, easy generation of an electrical signal, simple processing and storing of data, and the like, instead of a traditional analog scheme using a film while being grafted onto a semiconductor field. A digital based image technology strongly reflects a clinically environmental demand such as an early diagnosis of a disease on the basis of excellent diagnosis ability of a digital image.
Therefore, a “digital mammography”, which is a breast dedicated X-ray photographing technology capable of detecting a lesion and micro-calcification for detection and an early diagnosis of a breast cancer by representing an internal structure of the breast corresponding to an object to be inspected as a high resolution image, using unique biological tissue contrast capability of the X-ray, has been introduced. The digital mammography has been rapidly spread due to unique characteristics such as image enlargement, a decrease in the number of times of photographing, an increase in a resolution, and minimization of exposure through adjustment, of a luminance and a contrast ratio together with various advantages of the digital X-ray image technology.
A general mammography device mainly includes a support, column having a lower end portion fixed to a bottom and having a vertical column shape and a C-arm or a device body installed on the support column so as to ascend or descend in a vertical direction and generally having a C shape or a shape similar to the C shape in which a central portion thereof is configured to be rotatable around a horizontal axis. A generator irradiating an X-ray toward a lower end portion of the device body is mounted at an upper end portion of the device body, and a detector facing the generator is mounted at the lower end portion of the device body. A pressing pad that vertically and linearly reciprocates along an inner surface of the device body is installed between the generator and the detector.
In the mammography device as described above, when a subject is in a standing or sitting state at a photographing position, the device body ascends or descends and rotates with respect to the support column, such that a height and an angle of the device body are adjusted so that, a breast of the subject is put at a target position on the detector. Then, the pressing pad moves toward the detector to press the breast. In this state, the generator irradiates the X-ray toward the breast and the detector, and the detector positioned behind the breast receives the X-ray passing through the breast to obtain an image.
That is, the detector generates an electric signal for each position that is in proportion to an amount of incident X-ray, and reads the electrical signal and position information and processes the read electrical signal and position information by an image processing algorithm, thereby making it possible to obtain an X-ray image of the breast for a corresponding angle. Then, the above-process is repeated while rotating the generator and the detector with the breast interposed therebetween, whereby the mammography device may obtain high resolution images for the breast of the subject at various angles.
In a general mammography device having the above-mentioned photographing principle, a critical driving mechanical for minimizing discomfort of the subject and obtaining a high quality X-ray image is a pressing operation of the pressing pad and ascending or descending and rotating operations of the device body. Particularly, since the pressing pad applies direct pressure to the breast at the time of X-ray photographing, it is directly associated with pain and discomfort felt by the subject, and since the device body determines an accurate photographing position through ascent or descent and rotation, it is directly associated with quality of the X-ray image.
Here, the pressing pad presses the breast in order to photograph the breast in a state in which the breast, is pressed for the purpose of separating a lump (a lesion or a portion at which the possibility of micro-calcification is high) looking like being overlapped with a mammary gland, or the like, from the mammary gland. In order to accurately detect the lesion or the micro-calcification, the breast is generally photographed at various angles.
FIGS. 1 to 3 are schematic views illustrating a standard photographing method of a mammography device, wherein FIG. 1 illustrates a craniocaudal view (CC), and FIGS. 2 and 3 illustrate a mediolateral oblique view. FIGS. 4A to 4C are schematic views illustrating an operation mechanism of a general mammography photographing unit.
As illustrated in FIGS. 1 to 3, in the case of a standard mode, CC and MLO are performed on each of left and right breasts. For example, at least three views including RCC and RMLO are performed on the right breast, and at least three views including LCC and LMLO are performed on the left breast. In order to perform these views, the photographing unit of the mammography device should rotate at a corresponding angle.
Referring to FIGS. 4A to 4C, in a mammography device according to the related art, a shaft 12a of a device body 10 including a photographing unit is generally positioned in a state in which it is eccentric upwardly from the center of the device body 10 due to the center of gravity, or the like. Therefore, the device body 10 presses a breast BR, which is an object to be inspected, between a pressing pad 15 and a detector 14 at a position of FIG. 4A to perform the CC by a generator 13 and the detector 14. Then, in order to perform the MLO, the device body 10 should rotate at a desired angle θ as illustrated in FIG. 4B and then descend again by y so as to be appropriate for a height of the breast as illustrated in FIG. 4C. That is, the device body 10 performs a two-stage operation of rotation and descent.
In the mammography device according to the related art described above, a position and an angle of the mammography device are manually adjusted depending on a body shape (a height of a subject, a position of a breast, and the like) of a subject at the time of performing standard photographing, and linear movement and rotation of the device body are generally controlled separately, such that a rapid operation is not provided. For example, as described above, a height of the photographing unit is changed by rotation of the device body at the time of performing the MLO after performing the CC or at the time of performing the CC after performing the MLO. Then, the photographing unit should descend or ascend by the height changed by the rotation. Therefore, an accuracy may be decreased. Further, the subject should move backward from the mammography device in order to allow the device body to ascend or descend, and again enter a photographing position after the height is adjusted. For this reason, a photographing time of the mammography device becomes long, such that fatigue of the subject and an inspector is increased. In addition, it is difficult to obtain a bilaterally uniform photographing result due to a manual manipulation, such that a photographing accuracy is decreased.